Zoom lens, optical apparatus, and a manufacturing method of the zoom lens

ABSTRACT

A zoom lens includes, in order from an object, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group. Zooming is performed by changing respective distances between the first and second lens groups, the second and third lens groups, and the third and fourth lens groups. The first lens group includes a negative lens disposed closest to the object, and a negative lens. Specified conditional expressions are satisfied.

TECHNICAL FIELD

The present invention relates to a zoom lens, optical apparatus, and amanufacturing method of the zoom lens.

TECHNICAL BACKGROUND

Conventionally, small zoom lenses are proposed (for example, refer toPatent Document 1).

PRIOR ARTS LIST Patent Document

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2012-027283A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In recent years, regarding zoom lenses, an angle of view in a wide-angleend state is further expected to be widen while achieving downsizing.

The present invention is derived in view of such a problem, and aims toprovide a zoom lens, an optical apparatus, and a manufacturing method ofthe zoom lens which is small, however has a wide-angle of view in awide-angle end state with outstanding optical performance.

Means to Solve the Problems

In order to solve such a purpose, a zoom lens according to the presentinvention, comprises, in order from an object, a first lens group havinga negative refractive power, a second lens group having a positiverefractive power, a third lens group having a negative refractive power,and a fourth lens group having a positive refractive power, wherein thefirst lens group, the second lens group, the third lens group, and thefourth lens group move on an optical axis so that zooming is performedby changing distances between each lens group, wherein the first lensgroup comprises a negative lens disposed closest to the object, anegative lens, and a positive lens, wherein the following conditionalexpressions is satisfied:0.30<D3W/D3T<1.10however,

where D3W denotes an air interval between the third lens group and thefourth lens group in a wide-angle end state, and

D3T denotes an air interval between the third lens group and the fourthlens group in a telephoto end state.

In the zoom lens according to the present invention, it is preferablethat the following conditional expression is satisfied:0.50<M4/M3<1.00however,

where M3 denotes an amount of movement on the optical axis of the thirdlens group upon zooming from the wide-angle end state to the telephotoend state, and

M4 denotes an amount of movement on the optical axis of the fourth lensgroup upon zooming from the wide-angle end state to the telephoto endstate.

In the zoom lens according to the present invention, it is preferablethat the following conditional expression is satisfied:0.05<BFw/(fw ² +ft ²)^(1/2)<0.50however,

where BFw denotes an air equivalent distance from a lens rear endsurface of the zoom lens in the wide-angle end state to an image surfacethereof,

fw denotes a focal length of the zoom lens in the wide-angle end state,and

ft denotes a focal length of the zoom lens in the telephoto end state.

In the zoom lens according to the present invention, it is preferablethat the following conditional expression is satisfied:1.00<Σdw/Σdt<2.00however,

where Σdw denotes a distance from a lens front end surface to the lensrear end surface of the zoom lens in the wide-angle end state, and

Σdt denotes a distance from the lens front end surface to the lens rearend surface of the zoom lens in the telephoto end state.

In the zoom lens according to the present invention, it is preferablethat the first lens group is composed of, in order from the object, ameniscus-shaped negative lens having a concave surface facing an image,a biconcave negative lens, and a meniscus-shaped positive lens having aconvex surface facing the object.

In the zoom lens according to the present invention, it is preferablethat the fourth lens group is composed of one lens, wherein thefollowing conditional expression is satisfied:2.30<f4/fw<9.00however,

where f4 denotes a focal length of the fourth lens group, and

fw denotes a focal length of the zoom lens in the wide-angle end state.

In the zoom lens according to the present invention, it is preferablethat the following conditional expression is satisfied:0.80<(−f1)/f2<1.50however,

where f1 denotes a focal length of the first lens group, and

f2 denotes a focal length of the second lens group.

In the zoom lens according to the present invention, it is preferablethat the third lens group is composed of a cemented lens having anegative refractive power.

In the zoom lens according to the present invention, it is preferablethat the third lens group is composed of one negative lens.

In the zoom lens according to the present invention, it is preferablethat the second lens group comprises a positive lens closest to theobject.

In the zoom lens according to the present invention, it is preferablethat the second lens group comprises, in order from the object, apositive lens, a cemented lens which is composed of a positive lens anda negative lens.

In the zoom lens according to the present invention, it is preferablethat the second lens group comprises a positive lens closest to theobject, wherein the positive lens has an aspherical surface.

The optical apparatus according to the present invention is equippedwith any one of the above mentioned zoom lenses.

A manufacturing method of a zoom lens according to the present inventionis a manufacturing method of a zoom lens comprising, in order from anobject, a first lens group having a negative refractive power, a secondlens group having a positive refractive power, a third lens group havinga negative refractive power, and a fourth lens group having a positiverefractive power, wherein the first lens group, the second lens group,the third lens group, and the fourth lens group move on an optical axisso that zooming is performed by changing distances between each lensgroup thereof, wherein the first lens group comprises a negative lensdisposed closest to the object, a negative lens, and a positive lens,wherein each lens is arranged so that the following conditionalexpression is satisfied:0.30<D3W/D3T<1.10however,

where D3W denotes an air interval between the third lens group and thefourth lens group in the wide-angle end state, and

D3T denotes an air interval between the third lens group and the fourthlens group in the telephoto end state.

In the manufacturing method of the zoom lens according to the presentinvention, it is preferable that each lens is disposed in a lens-barrelso that the following conditional expression is satisfied:0.50<M4/M3<1.00however,

where M3 denotes an amount of movement on the optical axis of the thirdlens group upon zooming from the wide-angle end state to the telephotoend state, and

M4 denotes an amount of movement on the optical axis of the fourth lensgroup upon zooming from the wide-angle end state to the telephoto endstate.

In the manufacturing method of the zoom lens according to the presentinvention, it is preferable that each lens is arranged in thelens-barrel so that the following conditional expression is satisfied:0.05<BFw/(fw ² +ft ²)^(1/2)<0.50however,

where BFw denotes an air equivalent distance from the lens rear endsurface of the zoom lens in the wide-angle end state to an image surfacethereof,

fw denotes a focal length of the zoom lens in the wide-angle end state,and

ft denotes a focal length of the zoom lens in the telephoto end state.

In the manufacturing method of the zoom lens according to the presentinvention, it is preferable that each lens is arranged in thelens-barrel so that the following conditional expression is satisfied:1.00<Σdw/Σdt<2.00however,

where Σdw denotes a distance from the lens front end surface to the lensrear end surface of the zoom lens in the wide-angle end state thereof,and

Σdt denotes a distance from the lens front end surface to the lens rearend surface of the zoom lens in the telephoto end state thereof.

Advantageous Effects of the Invention

According to the present invention, it is possible to provide a zoomlens, an optical apparatus, and a manufacturing method of the zoom lenswhich is small, however has a wide-angle of view in the wide-angle endstate, and outstanding optical performance.

BRIEF DESCRIPTION THE DRAWINGS

FIGS. 1A to 1C are sectional views illustrating a configuration of azoom lens according to Example 1, where FIG. 1A depicts a position ofeach lens group in a wide-angle end state (W), FIG. 1B depicts that inan intermediate focal length state (A), and FIG. 1C depicts that in atelephoto end state (T).

FIGS. 2A to 2C illustrate graphs showing various aberrations of the zoomlens according to Example 1, where FIG. 2A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,FIG. 2B depicts those in the intermediate focal length state, and FIG.2C illustrates those in the telephoto end state.

FIGS. 3A to 3C are sectional views illustrating a configuration of azoom lens according to Example 2, where FIG. 3A depicts a position ofeach lens group in a wide-angle end state, FIG. 3B depicts that in anintermediate focal length state, and FIG. 3C depicts that in a telephotoend state.

FIGS. 4A to 4C illustrate graphs showing various aberrations of the zoomlens according to Example 2, where FIG. 4A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,FIG. 4B depicts those in the intermediate focal length state, and FIG.4C depicts those in the telephoto end state.

FIGS. 5A to 5C are sectional views illustrating a configuration of azoom lens according to Example 3, where FIG. 5A depicts a position ofeach lens group in a wide-angle end state, FIG. 5B depicts that in anintermediate focal length state, and FIG. 5C depicts that in a telephotoend state.

FIGS. 6A to 6C illustrate graphs showing various aberrations of the zoomlens according to Example 3, where FIG. 6A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,FIG. 6B depicts ones in the intermediate focal length state, and FIG. 6Cdepicts those in the telephoto end state.

FIGS. 7A to 7C are sectional views illustrating a configuration of azoom lens according to Example 4, where FIG. 7A depicts a position ofeach lens group in a wide-angle end state, FIG. 7B depicts that in anintermediate focal length state, and FIG. 7C depicts that in a telephotoend state.

FIGS. 8A to 8C illustrate graphs showing various aberrations of the zoomlens according to Example 4, where FIG. 8A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,FIG. 8B depicts those in the intermediate focal length state, and FIG.8C depicts those in the telephoto end state.

FIGS. 9A to 9C are sectional views illustrating a configuration of azoom lens according to Example 5, where FIG. 9A depicts a position ofeach lens group in a wide-angle end state, FIG. 9B depicts that in anintermediate focal length state, and FIG. 9C depicts that in a telephotoend state.

FIGS. 10A to 10C illustrate graphs showing various aberrations of thezoom lens according to Example 5, where FIG. 10A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,FIG. 10B depicts those in the intermediate focal length state, and FIG.10C depicts those in the telephoto end state.

FIGS. 11A to 11C are sectional views illustrating a configuration of azoom lens according to Example 6, where FIG. 11A depicts a position ofeach lens group in a wide-angle end state, FIG. 11B depicts that in anintermediate focal length state, and FIG. 11C depicts that in atelephoto end state.

FIGS. 12A, 12B and 12C illustrate graphs showing various aberrations ofthe zoom lens according to Example 6, where FIG. 12A depicts graphsshowing various aberrations upon focusing infinity in the wide-angle endstate, FIG. 12B depicts those in the intermediate focal length state,and FIG. 12C depicts those in the telephoto end state.

FIGS. 13A to 13C are sectional views illustrating a configuration of azoom lens according to Example 7, where FIG. 13A depicts a position ofeach lens group in a wide-angle end state, FIG. 13B depicts that in anintermediate focal length state, and FIG. 13C depicts that in atelephoto end state.

FIG. 14A to 14C illustrate graphs showing various aberrations of thezoom lens according to Example 7, where FIG. 14A depicts graphs showingvarious aberrations upon focusing infinity in the wide-angle end state,14B depicts those in the intermediate focal length state, and FIG. 14Cdepicts those in the telephoto end state.

FIG. 15A is a front elevation view of a digital still camera, and FIG.15B is a rear view of the digital still camera.

FIG. 16 is a sectional view along an arrow A-A′ in FIG. 15A.

FIG. 17 is a flowchart illustrating a manufacturing method of the zoomlens.

DESCRIPTION OF THE EMBODIMENT

An embodiment will now be explained with reference to the drawings. Azoom lens ZL according to the present embodiment comprises, in orderfrom an object as illustrated in FIGS. 1A to 1C, a first lens group G1having a negative refractive power, a second lens group G2 having apositive refractive power, a third lens group G3 having a negativerefractive power, and a fourth lens group G4 having a positiverefractive power, wherein the first lens group G1, the second lens groupG2, the third lens group G3, and the fourth lens group G4 move on anoptical axis so that zooming is performed by changing distances betweeneach lens group, wherein the first lens group G1 comprises a negativelens L11 disposed closest to the object, a negative lens, and a positivelens (corresponding to the lens L12 and the lens L13 in FIG. 1 , whereinthe following conditional expression (1) is satisfied.

Generally, in designing an imaging optical system such as a photographiclens, etc., it is difficult to attain downsizing synchronously whileenlarging an angle of view, in view of correcting various aberrations.However, according to the zoom lens ZL of the present embodiment, it ispossible to achieve downsizing while enlarging an angle of view, and toappropriately correct various aberrations such as spherical aberrationand coma aberration, etc.0.30<D3W/D3T<1.10  (1)however,

D3W denotes an air interval between the third lens group G3 and thefourth lens group G4 in the wide-angle end state, and

D3T denotes an air interval between the third lens group G3 and thefourth lens group G4 in the telephoto end state.

The conditional expression (1) is a conditional expression which definesan air interval between the third lens group G3 and the fourth lensgroup G4 in the wide-angle end state and the telephoto end state (adistance on the optical axis from a lens surface closest to the image ofthe third lens group G3 in the wide-angle end state, to a lens surfaceclosest to the object of the lens group G4). By satisfying with theconditional expression (1), it is possible to properly correct comaaberration, astigmatism, and lateral chromatic aberration whilesuppressing a change of an incident angle to the imaging surface byzooming. When deceeding the lower limit of the conditional expression(1), this is an advantageous in favor of correcting coma aberration,astigmatism and lateral chromatic aberration, however, since airintervals between the third lens group G3 and the fourth lens group G4greatly change in a wide-angle end state and in a telephoto end state,the change of the incident angle to the imaging surface upon zoomingbecomes great, thus it is not appreciated. When exceeding the upperlimit of the conditional expression (1), since it becomes difficult tocorrect coma aberration, astigmatism, and lateral chromatic aberrationwhile attaining downsizing, thus it is not appreciated.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the lower limit of the conditional expression (1)to 0.33. In order to ensure the advantageous effect of the presentembodiment, it is preferable to set the lower limit of the conditionalexpression (1) to 0.36.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the upper limit of the conditional expression (1)to 1.05. In order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit of the conditionalexpression (1) to 1.01.

Regarding the zoom lens ZL according to the present embodiment, it ispreferable that the following conditional expression (2) is satisfied:0.50<M4/M3<1.00  (2)however,

where M3 denotes an amount of movement on the optical axis of the thirdlens group G3 upon zooming from a wide-angle end state to a telephotoend state, and

M4 denotes an amount of movement on the optical axis of the fourth lensgroup G4 upon zooming from the wide-angle end state to the telephoto endstate.

A conditional expression (2) is a conditional expression which defines aratio of an amount of movement of the third lens group G3 and the fourthlens group G4 upon zooming from the wide-angle end state to thetelephoto end state. By satisfying the conditional expression (2), it ispossible to properly correct coma aberration, astigmatism and lateralchromatic aberration, while suppressing the change of the incident angleto the imaging surface. When deceeding the lower limit of theconditional expression (2), the third lens group G3 and the fourth lensgroup G4 are placed away from each other in the wide-angle end state, itis difficult to correct astigmatism and lateral chromatic aberration,thus this is not appreciated. When exceeding the upper limit of theconditional expression (2), this is advantageous for correctingchromatic aberration, etc., however, when performing a focus fordownsizing by the third lens group G3 or the forth lens group G4, therefractive power of a focal group must be improved, it is difficult tocorrect astigmatism and coma aberration, and it is not appreciated.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the upper limit of the conditional expression (2)to 0.996.

In the zoom lens ZL according to the present embodiment, it ispreferable that the following conditional expression (3) is satisfied:0.05<BFw/(fw ² +ft ²)^(1/2)<0.50  (3)however,

where BFw denotes an air equivalent distance from an lens rear endsurface of the zoom lens in the wide-angle end state ZL to an imagesurface thereof,

fw denotes a focal length of the zoom lens ZL in the wide-angle endstate, and

ft denotes a focal length of the zoom lens ZL in the telephoto endstate.

A conditional expression (3) is a conditional expression which definesan optical back focus for downsizing and an aberration correction in thezoom lens ZL of the present embodiment. When deceeding the lower limitof the conditional expression (3), it is advantageous for downsizing,however, since there is less distance in which a filter, etc. isdisposed between the lens rear end surface and the imaging surface, thusit is not appreciated. Moreover, astigmatism and coma aberration becomeworse. When exceeding the upper limit of the conditional expression (3),it is advantageous for disposing a filter, etc., however, it is notappreciated in view of downsizing. Moreover, astigmatism and comaaberration become worse.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the lower limit of the conditional expression (3)to 0.08. In order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit of the conditionalexpression (3) to 0.46.

Regarding the zoom lens ZL according to the present embodiment, it ispreferable that the following conditional expression (4) is satisfied:1.00<Σdw/Σdt<2.00  (4)however,

where Σdw denotes a distance from an lens front end surface to the lensrear end surface of the zoom lens ZL in the wide-angle end state, and

Σdt denotes a distance from the lens front end surface to the lens rearend surface of the zoom lens ZL in the telephoto end state.

The conditional expression (4) is a conditional expression which definesa change of the incident angle to the imaging surface upon zooming, anda change of a lens thickness appropriate to correct various aberrations.When deceeding the lower limit of the conditional expression (4), itbecomes advantageous for downsizing, however since the change of theincident angle to the imaging surface becomes large too much, thus it isnot appreciated. Moreover, spherical aberration and coma aberrationbecome worse. When exceeding the upper limit of the conditionalexpression (4), an incident angle to the imaging surface becomes small,however it is difficult to correct coma aberration and astigmatism, thusthis is not appreciated.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the lower limit of the conditional expression (4)to 1.03. In order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit of the conditionalexpression (4) to 1.55.

In the zoom lens ZL according to the present embodiment, it ispreferable that the first lens group is composed of, in order from theobject, a meniscus-shaped negative lens L11 having a concave surfacefacing the image, a biconcave negative lens L12, and a meniscus-shapepositive lens L13 having a convex surface facing the object.

With this arrangement, it is possible to properly correct imagingsurface curvature, astigmatism, and lateral chromatic aberration in alens whole system with an angle of view enlarged.

In the zoom lens ZL according to the present embodiment, it ispreferable that the fourth lens group G4 is composed of one lens, andthe following conditional expression (5) is satisfied:2.30<f4/fw<9.00  (5)however,

where f4 denotes a focal length of the fourth lens group G4, and

fw denotes a focal length of the zoom lens ZL in a wide-angle end state.

The conditional expression (5) is a conditional expression which definesan optimal focal length of the fourth lens group G4 most appropriatedfor downsizing of the lens and correcting various aberrations. Whendeceeding the lower limit of the conditional expression (5), since thefocal length of the fourth lens group G4 is too short and it isdisadvantageous for downsizing the lens, thus it is not appreciated.Moreover, coma aberration and imaging surface curvature become worse.When exceeding the upper limit of the conditional expression (5), it isadvantageous for downsizing, however, the incident angle to the imagingsurface becomes large, it is not appreciated. Moreover, coma aberrationand imaging surface curvature become worse.

In order to ensure the advantageous effect of the present embodiment, itis appreciated to set the lower limit of the conditional expression (5)to 2.50. In order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit of the conditionalexpression (5) to 8.00.

In the zoom lens ZL according to the present embodiment, it ispreferable that the following conditional expression (6) is satisfied:0.80<(−f1)/f2<1.50  (6)however,

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (6) is a conditional expression which definesa suitable focal length regarding the first lens group G1 and the secondlens group G2 in order to balance downsizing of the lens and correctingaberration. When deceeding the lower limit of the conditional expression(6), the focal length of the first lens group G1 is short in comparisonwith the focal length of the second lens group G2, thus, it is difficultto correct spherical aberration, and coma aberration, etc. whichoccurred in the first lens group G1, thus it is not appreciated. Whenexceeding the upper limit of the conditional expression (6), it isdisadvantageous for downsizing, thus it is not appreciated. Moreover,spherical aberration becomes worse.

In order to ensure the advantageous effect of the present embodiment, itis preferable to set the lower limit of the conditional expression (6)to 1.10. In order to ensure the advantageous effect of the presentembodiment, it is appreciated to set the upper limit of the conditionalexpression (6) to 1.20.

In the zoom lens ZL according to the present embodiment, it ispreferable that the third lens group G3 is composed of a cemented lenshaving a negative refractive power.

With this arrangement, it is possible to minimize a coma aberrationfluctuation and an imaging surface fluctuation when zooming, whiledownsizing a lens, and properly correct axial chromatic aberration and alateral chromatic aberration in a lens whole system.

In the zoom lens ZL according to the present embodiment, it ispreferable that the third lens group G3 is composed of one negativelens.

With this arrangement, it is possible to correct a coma aberrationfluctuation and imaging surface curvature fluctuation when zooming,while downsizing the lens.

In the zoom lens ZL according to the present embodiment, it ispreferable that the second lens group G2 has a positive lens L21 closestto the object.

With this arrangement, it is possible to properly correct sphericalaberration and coma aberration which occurred in the first lens groupG1.

In the zoom lens ZL according to the present embodiment, it isappreciated that the second lens group G2 has, in order from the object,a positive lens L21, and a cemented lens composed of a positive lens L22and a negative lens L23.

With this arrangement, it is possible to correct spherical aberration,astigmatism, coma aberration, and chromatic aberration while downsizingthe lens.

In the zoom lens ZL according to the present embodiment, it ispreferable that the positive lens L21 arranged closest to the objectwithin the second lens group G2 has an aspherical surface.

With this arrangement, it is possible to properly correct sphericalaberration, astigmatism, and coma aberration while downsizing a lens.

According to the zoom lens ZL of the present embodiment equipped withthe above configurations, although this is small, however it is possibleto realize a zoom lens with an angle of view enlarged in the wide-angleend state, and have outstanding optical performance.

FIGS. 15A and 15B and FIG. 16 illustrate configurations of a digitalstill camera CAM (optical apparatus) as an optical apparatus equippedwith the zoom lens ZL. In this digital still camera CAM, when a powerbutton is pressed, a not illustrated shutter of a photographing lens(zoom lens ZL) opens, light from a photographic subject (object) arecollected with the zoom lens ZL, and this is imaged by an image elementC (for instance, a CCD or a CMOS, etc.) disposed on an image surface I(refer to FIG. 1 ). The photographic subject image imaged by the imageelement C is displayed on a liquid crystal display monitor M providedbehind the digital still camera CAM. A photographer photos, afterdeciding a composition of a photographic subject image while looking atthe liquid crystal display monitor M, the photographic subject by theimage element C by pressing a shutter release button B1, and records andstores it in a not illustrated memory.

The camera CAM is provided with a fill light flushing unit EF whichemits fill light when a photographic subject is dark, and a functionbutton B2, etc. used for setting various conditions, etc. of the digitalstill camera CAM. Although a compact type camera in which a camera CAMand a zoom lens ZL are fabricated together is exampled herewith, it isapplicable to a single-lens reflex camera, as an optical apparatus, inwhich a lens-barrel having the zoom lens ZL is attachable and detachablewith a camera body.

According to the camera CAM of the present embodiment equipped with theabove configurations, by having the zoom lens ZL described above as aphotographing lens, although this is small, however it is possible torealize a camera with an angle of view in the wide-angle end stateenlarged, and having outstanding optical performance.

Next, referring to FIG. 17 , a manufacturing method of the zoom lens ZLdescribed above will be outlined. Firstly, each lens is disposed so thatthe first lens group G1 having a negative refractive power, the secondlens group G2 having a positive refractive power, the third lens groupG3 having a negative refractive power, and the fourth lens G4 having apositive refractive power are arranged in order from the object in alens-barrel (Step ST10). Here, each lens is arranged so that zooming isperformed by changing distances between each lens group by moving thefirst lens group G1, the second lens group G2, the third lens group G3,and the fourth lens group G4 on the optical-axis (Step ST20). The firstlens group G1 is arranged so that this has a negative lens L11 arrangedclosest to the object, a negative lens, and a positive lens (Step ST30).Each lens is arranged so that the following conditional expression (1)is satisfied (Step ST40):0.30<D3W/D3T<1.10  (1)however,

where D3W denotes an air interval between the third lens group G3 andthe fourth lens group G4 in the wide-angle end state, and

D3T denotes an air interval between the third lens group G3 and thefourth lens group G4 in the telephoto end state.

In the manufacturing method of the zoom lens ZL according to the presentembodiment, it is preferable to arrange each lens in the lens-barrel sothat the above-mentioned conditional expression (2) is satisfied.

In the manufacturing method of the zoom lens ZL according to the presentembodiment, it is preferable to arrange each lens in the lens-barrel sothat the above-mentioned conditional expression (3) is satisfied.

In the manufacturing method of the zoom lens ZL according to the presentembodiment, it is preferable to arrange each lens in the lens-barrel sothat the above-mentioned conditional expression (4) is satisfied.

Specifically speaking, in the present embodiment, for example in orderfrom the object as illustrated in FIGS. 1A to 1C, the first lens groupG1 is composed of the meniscus-shaped negative lens L11 having a concavesurface facing the image, the biconcave negative lens L12, themeniscus-shaped positive lens L13 having a concave surface facing theobject, the second lens group G2 is composed of the biconvex positivelens L21, an aperture stop S aiming at adjusting a quantity of light,the cemented lens composed of the biconvex positive lens L22 and thebiconcave negative lens L23, the biconvex positive lens L24, and thebiconvex positive lens L25, the third lens group G3 is composed of themeniscus-shaped negative lens L31 having a concave surface facing theimage, and the forth lens group G4 is composed of the meniscus-shapedpositive lens L41 having a convex surface facing the object. Each lensis disposed as mentioned above, the zoom lens ZL is manufactured.

According to the manufacturing method of the zoom lens ZL, although thisis small, however it is possible to realize a zoom lens with an angle ofview in the wide-angle end state enlarged, and having outstandingoptical performance.

EXAMPLE

Next, each example according to the present embodiment is describedreferring to the drawings. Tables 1 to 7 are illustrated below, andthese show tables of each data in Examples 1 to 7.

Note that each reference sign to FIGS. 1A to 1C according to Example 1is independently used for each example in order to avoid the complicatedexplanation due to increasing the digit number of reference signs.Therefore, even if referred to the same reference sings shared withother drawings according to other examples, this does not necessarilymean they are the same configurations of the other examples.

In each example, as calculation targets of aberration characteristics,C-line (wave length of 656.2730 nm), d-line (wave length of 587.5620nm), F-line (wave length of 486.1330 nm), and g-line (wave length of435.8350 nm) are selected.

In [General Data] in tables, f means a focal length of the lens wholesystem, Fno means a F number, ω means a half angle of view (maximumincident angle, unit: degree), Y means an image height, BF means a backfocus (what is carried out by performing air equivalent of a distancefrom a lens rear end surface to a paraxial image surface on the opticalaxis), and TL means a total lens length (what is added with BF to adistance from a lens front end surface to a lens rear end surface on theoptical axis).

In [Lens Data] in tables, a surface number means an order of an opticalsurface from the object side along a direction in which a ray travels, Rmeans a radius of curvature of each optical surface, D means a distanceto the next lens surface, which is a distance on the optical axis fromeach optical surface to the next optical surface (or an image surface),nd means a refractive index to d-line of material of an optical member,and vd means an Abbe number on the basis of the d-line of material ofthe optical member. An object surface means a surface of an object,(variable) means a variable distance to the next lens surface, “∞” meansa plane or an aperture, (stop S) means an aperture stop S, and an imagesurface means an image surface I. The refractive index of an air“1.00000” is omitted. In case that an optical surface has an asphericalsurface, an “*” sign is given to the surface number, and a paraxialradius of curvature is illustrated in columns of the radius of curvatureR.

In [aspherical surface data] in tables, regarding the aspherical surfaceshown in [Lens Data], its configuration is indicated with the followingexpression (a). X(y) means a distance along the optical axis from atangent plane in a vertex of an aspherical surface to a location on theaspherical surface in height y, R means a radius of curvature (paraxialradius of curvature) of a standard spherical surface, κ means a coneconstant, and Ai means an i-th aspherical surface coefficient. “E-n”means “x10^(−n).” For instance, 1.234E-05 is equal to 1.234×10⁻⁵.X(y)=(y ² /R)/{1+(1−κ×y ² /R ²)^(1/2) }+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (a)

[variable distance data] in tables show values Di of a valuable distancein each state such as a wide-angle end, an intermediate focal length, ora telephoto end. Note that Di indicates a variable distance between thei-th surface and the (i+1)-th surface.

In [Lens Group Data] in tables, G means a group number, a group firstsurface means a surface number closest to an object of each group, agroup focal length means a focal length of each group, and a lensconfiguration length means a distance on the optical axis from a lenssurface closest to the object in each group to a lens surface closest tothe image.

[Conditional Expression] in tables shows values corresponding to theconditional expressions (1) to (6).

Hereinafter, in all general data values, regarding the focal length fshown, a radius of curvature R, a distance to the next lens surface D,and other lengths, etc. “mm” is generally used except a specificrequest, however a zoom lens is not limited to the above, sinceequivalent optical performance can be obtained even if the zoom lens isproportionally enlarged or proportionally shrunk. Moreover, the unit isnot limited to “mm,” can be used with another appropriate unit.

The explanations concerning the tables are common among all theexamples, thus hereinafter the explanations are omitted.

Example 1

Example 1 is described using FIGS. 1A to 1C and 2A to 2C, and Table 1.The zoom lens ZL (ZL1) according to Example 1 is composed of, in orderfrom the object as shown in FIGS. 1A to 1C, a first lens group G1 havinga negative refractive power, a second lens group G2 having a positiverefractive power, a third lens group G3 having a negative refractivepower, and a fourth lens group G4 having a positive refractive power.

The first lens group G1 is composed of, in order from an object, ameniscus-shaped negative lens L11 having a concave surface facing animage, a biconcave negative lens L12, and a meniscus-shaped positivelens L13 having a convex surface facing an object. Note that an imageside surface of the negative lens L11 has an aspherical surface.

The second lens group G2 is composed of, in order from an object, abiconvex positive lens L21, an aperture stop S aiming at adjusting aquantity of light, a cemented lens composed of a biconcave positive lensL22 and a biconcave negative lens L23, a biconvex positive lens L24, anda biconvex positive lens L25. Note that both side surfaces of thepositive lens L21 have an aspherical surface. Moreover, an image sidesurface of the positive lens L24 has an aspherical surface.

The third lens group G3 is composed of a meniscus-shaped negative lensesL31 having a concave surface facing the image.

The fourth lens group G4 is composed of a meniscus-shaped positivelenses L41 having a convex surface facing the object. Note that anobject side surface of the positive lens L41 has an aspherical surface.

A filter group FL is disposed on the image side of the fourth lens groupG4, and is composed of low pass filters, infrared cut filters, etc. forcutting spatial frequency more than marginal resolution of a solid-stateimage sensing device, such as CCDs disposed on the image surface I.

In the zoom lens ZL1 according to the present example, all the lensgroups from the first lens group G1 to the fourth lens group G4 moveupon zooming from a wide-angle end state (W) to a telephoto end state(T) so that distances between each lens group change. Specificallyspeaking, the first lens group G1 once moves to the image side in amanner of drawing a locus of a convex on the image side, afterwardsmoves to the object side. The second lens group G2 moves to the objectside. The third lens group G3 moves to the object side. The fourth lensgroup G4 moves to the object side. At this point, a distance between thefirst lens group G1 and the second lens group G2 decreases, a distancebetween the second lens group G2 and the third lens group G3 decreases,and a distance between the third lens group G3 and the fourth lens groupG4 increases.

Values of each data in Example 1 are shown in Table 1 below. The surfacenumbers 1 to 24 in Table 1 correspond to each optical surface of m1 tom24 indicated in FIGS. 1A to 1C.

TABLE 1 [General Data] Zoom ratio 2.77 Wide-angle Intermediate end focalpoint Telephoto end f 1.00 1.53 2.77 Fno 3.39 4.15 5.96 ω 43.1 30.4 17.9Y 0.89 0.89 0.89 BF 0.57 0.88 1.65 TL 5.44 5.03 5.53 [Lens Data] Surfacenumber R D nd νd Object Surface ∞  1  2.7607 0.0859 1.80610 40.74 *2 0.7655 0.5706  3 −5.9880 0.0675 1.58913 61.22  4  7.5124 0.0123  5 1.7607 0.2147 1.80809 22.74  6  5.0958 D6 (variable) *7  0.8712 0.17181.58913 61.20 *8 −7.6237 0.0123  9 ∞ 0.1350 (stop S) 10  0.8747 0.22701.52249 59.21 11 −1.9759 0.0491 1.80100 34.92 12  0.6513 0.0982 13 4.9080 0.0920 1.58913 61.20 *14 −8.9252 0.0307 15  4.9080 0.13501.48749 70.31 16 −2.1650 D16 (variable) 17  6.1350 0.0613 1.58913 61.2218  2.1027 D18 (variable) *19  3.0675 0.1595 1.58913 61.20 20  8.9701D20 (variable) 21 ∞ 0.0429 1.51680 64.20 22 ∞ 0.0920 23 ∞ 0.0429 1.5168064.20 24 ∞ 0.0307 Image Surface ∞ [Aspherical surface data] SurfaceNumber κ A4 A6 A8 A10  2 0.5552  1.82699E−02 4.51869E−02 0.00000E+000.00000E+00  7 0.2252  4.23003E−02 3.15591E−02 0.00000E+00 0.00000E+00 8 1.0000 −7.49496E−03 0.00000E+00 0.00000E+00 0.00000E+00 14 1.0000 7.27866E−02 0.00000E+00 0.00000E+00 0.00000E+00 19 1.0000 −1.58968E−031.35218E−02 0.00000E+00 0.00000E+00 [Zooming Data] Variable Wide-angleIntermediate distance end focal point Telephoto end D6 1.85061 0.918550.13347 D16 0.4329 0.40719 0.34254 D18 0.47104 0.70238 1.28429 D200.38777 0.69622 1.47210 [Lens group data] Group Group Group Lensconfiguration number first surface focal length length G1 1 −1.766430.9510 G2 7 1.50036 0.9511 G3 17 −5.46114 0.0613 G4 19 7.83422 0.1595[Conditional expression] Conditional expression (1) D3W/D3T = 0.367Conditional expression (2) M3/M4 = 0.571 Conditional expression (3) BFw/(fw² + ft²)^(1/2) = 0.192 Conditional expression (4) Σdw/Σdt = 1.256Conditional expression (5) f4/fw = 7.834 Conditional expression (6)(−f1)/f2 = 1.177

As shown in Table 1, it is understandable that the conditionalexpressions (1) to (6) are satisfied regarding the zoom lens ZL1according to the present example.

FIG. 2A to 2C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of zoom lens ZL1 according to Example 1.FIG. 2A illustrates graphs showing various aberrations upon focusing oninfinity in the wide-angle end state of Example 1, FIG. 2B illustratesgraphs showing various aberrations upon focusing on infinity in theintermediate focal length state of Example 1, and FIG. 2C illustratesgraphs showing various aberrations upon focusing on infinity in thetelephoto end state of Example 1.

In each graph showing aberration, FNO means a F number, and A means ahalf angle of view against each image height (unit: degree). d meansd-line, g means g-line, C means C-line, and F means aberration inF-line. Moreover, what is not described means aberration according tod-line. In graphs showing astigmatism, a solid line indicates a sagittalimage plane and a dashed line indicates a meridional image plane. Notethat also in graphs showing aberration of each example described below,the same signs are used as those in the present example.

As is obvious in each graph showing aberration, in the zoom lens ZL1according to Example 1, it is understandable that various aberrationsare properly corrected, and this has outstanding optical performance.

Example 2

Example 2 is explained using FIGS. 3A to 3C and 4A to 4C, and Table 2.The zoom lens ZL (ZL2) according to Example 2 is composed of, in orderfrom an object as shown in FIG. 3 , a first lens group G1 having anegative refractive power, a second lens group G2 having a positiverefractive power, a third lens group G3 having a negative refractivepower, and a fourth lens group G4 having a positive refractive power.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing theimage, a biconcave negative lens L12, and a meniscus-shaped positivelens L13 having a convex surface facing the object. Note that an imageside surface of the negative lens L11 has an aspherical surface.

The second lens group G2 is composed of, in order from the object, anaperture stop S aiming at adjusting a quantity of light, a biconvexpositive lens L21, and a cemented lens of a biconvex positive lens L22and a biconcave negative lens L23, and a biconvex positive lens L24.Note that both side surfaces of the positive lens L21 have an asphericalsurface.

The third lens group G3 is composed of a biconcave negative lenses L31.

The fourth lens group G4 is composed of a meniscus-shaped positivelenses L41 having a convex surface facing the object. Note that anobject side surface of the positive lens L41 has an aspherical surface.

The filter group FL is arranged on the image side of the fourth lensgroup G4, and is composed of a low pass filter, an infrared cut filter,etc. for cutting a spatial frequency more than marginal resolution of asolid-state image sensing device such as a CCD disposed on the imagesurface I.

In the zoom lens ZL2 according to the present example, all the lensgroups from the first lens group G1 to the fourth lens group G4 moveupon zooming from the wide-angle end state (W) to the telephoto endstate (T) so that distances between each lens group change. Specificallyspeaking, the first lens group G1 once moves to the image side in amanner of drawing a locus of a convex on the image side, afterwards,moves to the object side. The second lens group G2 moves to the objectside. The third lens group G3 moves to the object side. The fourth lensgroup G4 moves to the object side. At this point, a distance between thefirst lens group G1 and the second lens group G2 decreases, a distancebetween the second lens group G2 and the third lens group G3 decreases,and a distance between the third lens group G3 and the fourth lens groupG4 increases.

Values of each data in Example 2 are shown in Table 2 below. The surfacenumbers 1 to 22 in Table 2 correspond to each optical surface of m1 tom22 which are illustrated in FIGS. 3A to 3C.

TABLE 2 [General Data] Zoom ratio 2.94 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.53 2.94 Fno 3.03 3.99 6.03 ω 43.2 30.7 16.9Y 0.89 0.89 0.89 BF 1.04 1.63 3.29 TL 5.97 5.65 6.48 [Lens Data] Surfacenumber R D nd νd Object surface ∞  1 2.2883 0.0920 1.80610 40.74 *20.7373 0.6564  3 −9.1361 0.0675 1.72916 54.61  4 3.9033 0.0123  5 1.73620.2331 1.80809 22.74  6 6.0369 D6 (variable)  7 ∞ 0.0307 (stop S) *80.8589 0.2822 1.58913 61.20 *9 −7.2780 0.0491 10 1.6834 0.2331 1.5826746.48 11 −1.8084 0.0675 1.80100 34.92 12 0.7855 0.0859 13 2.5700 0.20251.48749 70.31 14 −1.2299 D14 (variable) 15 −7.9755 0.0736 1.67300 38.1516 5.2416 D16 (variable) *17 2.8221 0.1411 1.58913 61.22 18 6.9412 D18(variable) 19 ∞ 0.0429 1.51680 64.20 20 ∞ 0.0920 21 ∞ 0.0429 1.5168064.20 22 ∞ 0.0307 Image surface ∞ [Aspherical surface data] Surfacenumber κ A4 A6 A8 A10  2 0.5876  1.48400E−02 2.93833E−02 0.00000E+000.00000E+00  8 0.5920 −1.48182E−02 0.00000E+00 1.22878E−01 3.62602E−02 9 1.0000  9.86346E−02 0.00000E+00 0.00000E+00 0.00000E+00 17 1.0000−1.85798E−02 6.87964E−03 0.00000E+00 0.00000E+00 [Zooming data] VariableWide-angle Intermediate distance end focal point Telephoto end D61.90212 0.98604 0.16214 D14 0.41369 0.35509 0.19202 D16 0.38614 0.444740.60782 D18 0.86120 1.45446 3.10802 [Lens group data] Group Group firstGroup focal Lens configuration number surface length length G1 1−1.60069 1.0613 G2 7 1.54986 0.9510 G3 15 −4.68917 0.0736 G4 17 7.970970.1411 [Conditional expression] Conditional expression (1) D3W/D3T =0.868 Conditional expression (2) M3/M4 = 0.910 Conditional expression(3) BFw/( fw² + ft²)^(1/2) = 0.335 Conditional expression (4) Σdw/Σdt =1.546 Conditional expression (5) f4/fw = 7.971 Conditional expression(6) (−f1)/f2 = 1.033

Based on Table 2, the conditional expressions (1) to (6) are satisfiedregarding the zoom lens ZL2 according to the present example.

FIGS. 4A, 4B and 4C illustrate graphs showing various aberrations(spherical aberration, astigmatism, distortion aberration, comaaberration, and lateral chromatic aberration) of zoom lens ZL2 accordingto Example 2. FIG. 4A illustrates graphs showing various aberrationsupon focusing on infinity in the wide-angle end state of Example 2, FIG.4B illustrates graphs showing various aberrations upon focusing oninfinity in the intermediate focal length state of Example 2, and FIG.4C illustrates graphs showing various aberrations upon focusing oninfinity in the telephoto end state of Example 2. As is obvious in eachgraph showing aberration, in the zoom lens ZL2 according to Example 2,it is understandable that various aberrations are properly corrected,and this has outstanding optical performance.

Example 3

Example 3 is explained using FIGS. 5A to 5C and 6A to 6C, and Table 3.The zoom lens ZL (ZL3) according to Example 3 is composed of, in orderfrom the object as shown in FIGS. 5A to 5C, a first lens group G1 havinga negative refractive power, a second lens group G2 having a positiverefractive power, a third lens group G3 having a negative refractivepower, and a fourth lens group G4 having a positive refractive power.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing animage side, a biconcave negative lens L12, and a meniscus-shapedpositive lens L13 having a concave surface facing the object. Note thatan image side surface of the negative lens L11 has an asphericalsurface.

The second lens group G2 is composed of, in order from the object, abiconvex positive lens L21, an aperture stop S aiming at adjusting aquantity of light, a cemented lens composed of a biconvex positive lensL22 and a biconcave negative lens L23, a biconvex positive lens L24, anda biconvex positive lens L25. Note that both side surfaces of thepositive lens L21 have an aspherical surface.

The third lens group G3 is composed of a biconcave negative lenses L31.

The fourth lens group G4 is composed of a meniscus-shaped positivelenses L41 having a convex surface facing the object side. Note that anobject side surface of the positive lens L41 has an aspherical surface.

The filter group FL is arranged on the image side of the fourth lensgroup G4, and is composed of a low pass filter, an infrared cut filter,etc. for cutting a spatial frequency more than marginal resolution of asolid-state image sensing device, such as a CCD disposed on the imagesurface I.

In the zoom lens ZL3 according to the present example, all the lensgroups from the first lens group G1 to the fourth lens group G4 moveupon zooming from the wide-angle end state to the telephoto end state sothat distances between each lens group change. Specifically speaking,the first lens group G1 once moves to the image side in a manner ofdrawing a locus of a convex, afterwards moves to the object side. Thesecond lens group G2 moves to the object side. The third lens group G3moves to the object side. The fourth lens group G4 moves to the objectside. At this point, a distance between the first lens group G1 and thesecond lens group G2 decreases, and a distance between the second lensgroup G2 and the third lens group G3 increases.

Values of each data in Example 3 are shown in Table 3 below. The surfacenumbers 1 to 24 in Table 3 correspond to each optical surface of m1 tom24 which are shown in FIGS. 5A to 5C.

TABLE 3 [General Data] Zoom ratio 3.37 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.53 3.37 Fno 2.89 3.57 5.87 ω 44.0 30.8 14.8Y 0.81 0.85 0.89 BF 1.29 1.62 2.88 TL 5.51 5.15 5.72 [Lens Data] Surfacenumber R D nd νd Object surface ∞  1 3.0676 0.0736 1.80610 40.77 *20.8660 0.5399  3 −3.5156 0.0614 1.72916 54.61  4 7.1326 0.0123  5 2.02470.1902 1.80809 22.74  6 13.1350 D6 (variable) *7 0.9075 0.2209 1.5920167.05 *8 −9.6052 0.1411  9 ∞ 0.0123 (stop S) 10 0.9301 0.1902 1.6229958.12 11 −4.1799 0.0491 1.80100 34.92 12 0.6440 0.0982 13 4.9082 0.08591.58913 61.22 14 −4.9775 0.0307 15 3.0676 0.0920 1.58913 61.22 16−10.3052 D16 (variable) 17 −6.1353 0.0491 1.58913 61.22 18 3.4411 D18(variable) *19 2.4541 0.1104 1.62263 58.19 20 5.4478 D20 (variable) 21 ∞0.0430 1.51680 64.20 22 ∞ 0.0920 23 ∞ 0.0430 1.51680 64.20 24 ∞ 0.0307Image surface ∞ [Aspherical surface data] Surface number κ A4 A6 A8 A102 0.8145  6.24280E−03  2.17041E−02  0.00000E+00 0.00000E+00 7 1.0000−1.15156E−01 −6.71093E−02 −1.33516E−01 0.00000E+00 8 1.0000  4.43207E−03 0.00000E+00  0.00000E+00 0.00000E+00 19 1.0000 −2.42479E−02 2.00563E−02  9.42333E−02 0.00000E+00 [Zooming data] VariableIntermediate distance Wide-angle end focal point Telephoto end D61.90947 1.03034 0.04886 D16 0.07479 0.13747 0.49243 D18 0.27637 0.406120.33772 D20 1.11507 1.43886 2.70424 [Lens group data] Group Group firstGroup focal Lens configuration number surface length length G1 1−1.63500 0.8773 G2 7 1.41112 0.9203 G3 17 −3.73503 0.0491 G4 19 7.072570.1104 [Conditional expression] Conditional expression (1) D3W/D3T =0.818 Conditional expression (2) M3/M4 = 0.963 Conditional expression(3) BFw/( fw² + ft²)^(1/2) = 0.368 Conditional expression (4) Σdw/Σdt =1.487 Conditional expression (5) f4/fw = 7.073 Conditional expression(6) (−f1)/f2 = 1.159

Based on Table 3, regarding zoom lens ZL3 according to the presentexample the conditional expressions (1) to (6) are satisfied.

FIG. 6A to 6C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of zoom lens ZL3 according to Example 3.FIG. 6A illustrates graphs showing various aberrations upon focusing oninfinity in the wide-angle end state of Example 3, FIG. 6B illustratesgraphs showing various aberrations upon focusing on infinity in theintermediate focal length state of Example 3, and FIG. 6C illustratesgraphs showing various aberrations upon focusing on infinity in thetelephoto end state of Example 3. As is obvious in each graphs showingaberration, in the zoom lens ZL3 according to Example 3, it isunderstandable that various aberrations are properly corrected, and thishas outstanding optical performance.

Example 4

Example 4 is explained using FIGS. 7A to 7C, FIG. 8A to 8C, and Table 4.The zoom lens ZL (ZL4) according to Example 4 is composed of, in orderfrom an object as shown in FIGS. 7A to 7C, a first lens group G1 havinga negative refractive power, a second lens group G2 having a positiverefractive power, a third lens group G3 having a negative refractivepower, a fourth lens group G4 having a positive refractive power, and afifth lens group G5 having a negative refractive power.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing theimage, a biconcave negative lens L12, and a meniscus-shaped positivelens L13 having a convex facing the object. Note that an object sidesurface of the negative lens L11 has an aspherical surface. Moreover, animage side surface of the positive lens L12 has an aspherical surface.

The second lens group G2 is composed of, in order from the object, anaperture stop S aiming at adjusting a quantity of light, a biconvexpositive lens L21, a cemented lens composed of a meniscus-shapedpositive lens L22 having a convex surface facing the object and ameniscus-shaped negative lens L23 having a concave surface facing theimage, a cemented lens composed of a meniscus-shaped negative-lens lensL24 having a concave surface facing the image and a biconvex positivelens L25. Note that both side surfaces of the positive lens L21 have anaspherical surface.

The third lens group G3 is composed of a biconcave negative lenses L31.Note that an image side surface of the negative lens L31 has anaspherical surface.

The fourth lens group G4 is composed of a biconvex positive lenses L41.

The fifth lens group G5 is composed of a meniscus-shaped negative lensesL51 having a concave surface facing the object.

The filter group FL is arranged on the image side of the fifth lensgroup G5, and is composed of a low pass filter, an infrared cut filter,etc. for cutting spatial frequency more than marginal resolution of asolid-state image sensing device such as a CCD disposed on the imagesurface I.

Regarding the zoom lens ZL4 according to the present example, uponzooming from the wide-angle end state (W) to the telephoto end state(T), the first lens group G1 to the fourth lens group G4 move so thatdistances between each lens group change. Specifically speaking, thefirst lens group G1 once moves to the image side in a manner of drawinga locus of a convex, and moves to the image side. The second lens groupG2 moves to the object side. The third lens group G3 moves to the imageside. The fourth lens group G4 moves to the image side. The fifth lensgroup G5 is fixed. At this point, a distance between the first lensgroup G1 and the second lens group G2 decreases, a distance between thesecond lens group G2 and the third lens group G3 increases, a distancebetween the third lens group G3 and the fourth lens group G4 onceincreases and afterwards decreases, and a distance between the fourthlens group G4 and the fifth lens group G5 decreases.

Values of each data in Example 4 are shown in Table 4 below. The surfacenumbers 1 to 25 in Table 4 correspond to each optical surface of m1 tom25 which are indicated in FIGS. 7A to 7C.

TABLE 4 [General Data] Zoom ratio 2.61 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.58 2.61 Fno 1.88 2.36 2.88 ω 51.5 38.6 24.0Y 1.044 1.187 1.187 BF 0.38 0.38 0.38 TL 9.67 9.08 9.33 [Lens Data]Surface number R D nd νd Object surface ∞ *1 8.64261 0.21739 1.6968055.52  2 1.44928 1.05797  3 −5.58998 0.11594 1.59201 67.02 *4 4.191790.30379  5 4.84283 0.30436 1.84666 23.80  6 −67.97868 D6 (variable)  7 ∞0.07246 (stop S) *8 1.86965 0.44802 1.72903 54.04 *9 −7.50935 0.02898 103.22848 0.23509 1.49700 81.73 11 9.75758 0.08695 1.64769 33.72 121.73854 0.38272 13 23.07107 0.08696 1.74950 35.25 14 1.45638 0.557361.49700 81.73 15 −2.17480 D15 (variable) 16 −167.23232 0.11594 1.7130053.94 *17 17.28659 D17 (variable) 18 13.39219 0.51738 1.72916 54.61 19−2.76740 D19 (variable) 20 −2.76850 0.11594 1.48749 70.32 21 −20.233440.02899 22 ∞ 0.06812 1.51680 64.20 23 ∞ 0.02174 24 ∞ 0.10145 1.5168064.20 25 ∞ 0.21740 Image surface ∞ [Aspherical surface data] Surfacenumber κ A4 A6 A8 A10 1 1.0000  1.26979E−02 −1.33695E−03  5.16445E−050.00000E+00 4 1.0000 −3.36717E−03 −1.25425E−03 −1.81979E−03 0.00000E+008 1.0000 −1.52678E−02  7.22094E−04 −4.02217E−04 0.00000E+00 9 1.0000 2.01074E−02  0.00000E+00  0.00000E+00 0.00000E+00 17 1.0000 2.34398E−02  4.67999E−04  7.54536E−04 0.00000E+00 [Zooming data]Variable Intermediate distance Wide-angle end focal point Telephoto endD6 2.91460 1.45214 0.47826 D15 0.14493 1.16020 2.80044 D17 0.813900.85831 0.81112 D19 0.74153 0.58058 0.21655 [Lens group data] GroupGroup first Group focal Lens configuration number surface length lengthG1 1 −2.30358 1.99945 G2 8 2.66160 1.89854 G3 16 −21.96771 0.11594 G4 183.18841 0.51738 G5 20 −6.59368 0.11594 [Conditional expression]Conditional expression (1) D3W/D3T = 1.003 Conditional expression (2)M3/M4 = 0.995 Conditional expression (3) BFw/(fw² + ft²)^(1/2) = 0.126Conditional expression (4) Σdw/Σdt = 1.038 Conditional expression (5)f4/fw = 3.188 Conditional expression (6) (−f1)/f2 = 0.865

According to Table 4, it is understandable that the zoom lens ZL4according to the present example is satisfied with the conditionalexpressions (1) to (6).

FIG. 8A to 8C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of zoom lens ZL4 according to Example 4.FIG. 8A illustrates graphs showing various aberrations upon focusing oninfinity in the wide-angle end state of Example 4, FIG. 8B illustratesgraphs showing various aberrations upon focusing on infinity in theintermediate focal length state of Example 4, and FIG. 8C illustratesgraphs showing various aberrations upon focusing on infinity in thetelephoto end state of Example 4.

As is obvious in each graph of the various aberrations, it isunderstandable that the zoom lens ZL4 according to Example 4 is properlycorrected with various aberrations, and has outstanding opticalperformance.

Example 5

Example 5 is explained using FIGS. 9A to 9C, FIG. 10A to 10C, and Table5. The zoom lens ZL (ZL5) according to Example 5 is composed of, inorder from an object as shown in FIGS. 9A to 9C, a first lens group G1having a negative refractive power, a second lens group G2 having apositive refractive power, a third lens group G3 having a negativerefractive power, and a fourth lens group G4 having a positiverefractive power.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing animage, a biconcave negative lens L12, a cemented lenses composed of ameniscus-shaped positive lens L13 having a convex surface facing theobject and a meniscus-shaped negative lens L14 having a concave surfacefacing the image. Note that both side surfaces of the negative lens L11have an aspherical surface. Moreover, both side surfaces of the negativelens L12 have an aspherical surface.

The second lens group G2 is composed of, in order from the object, anaperture stop S aiming at adjusting the quantity of light, a biconvexpositive lens L21, a cemented lens composed of a biconvex positive lensL22 and a biconcave negative lens L23, and a biconvex positive lens L24.Note that both side surfaces of the positive lens L21 have an asphericalsurface.

The third lens group G3 is composed of a meniscus-shaped negative lensesL31 having a concave surface facing the image. Note that an image sidesurface of the positive lens L31 has an aspherical surface.

The fourth lens group G4 is composed of a biconvex positive lenses L41.Note that an object side surface of the positive lens L41 has anaspherical surface.

The filter group FL is arranged on the image side of the fourth lensgroup G4, and is composed of a low pass filter, an infrared cut filter,etc. for cutting spatial frequency more than marginal resolutions of asolid-state image sensing device, such as a CCD disposed on the imagesurface I.

Regarding the zoom lens ZL5 according to the present example, uponzooming from the wide-angle end state (W) to the telephoto end state(T), the lens groups from the first lens group G1 to the fourth lensgroup G4 move so that distances between each lens group change.Specifically speaking, the first lens group G1 moves to the image side.The second lens group G2 moves to the object side. The third lens groupG3 moves to the object side. The fourth lens group G4 moves to theobject side. At this point, a distance between the first lens group G1and the second lens group G2 decreases, a distance between the secondlens group G2 and the third lens group G3 increases, and a distancebetween the third lens group G3 and the fourth lens group G4 increases.

Value of each example in Example 5 is shown in Table 5 below. Thesurface numbers 1 to 23 in Table 5 correspond to each optical surface ofm1 to m23 shown in FIGS. 9A to 9C.

TABLE 5 [General Data] Zoom ratio 2.29 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.44 2.29 Fno 1.86 2.38 2.88 ω 42.1 34.0 21.4Y 0.766 0.909 0.909 BF 0.98 0.95 0.99 TL 7.55 6.61 6.14 [Lens Data]Surface number R D nd νd Object surface ∞ *1 4.4948 0.0888 1.69680 55.46*2 1.0157 0.6109 *3 −5.3145 0.0888 1.59201 67.02 *4 12.6805 0.0222  52.3141 0.2325 2.00069 25.46  6 5.0164 0.0666 1.69680 55.52  7 3.8665 D7(variable)  8 ∞ 0.0555 (stop S) *9 1.5142 0.4439 1.77250 49.50 *10−8.8479 0.0927 11 1.9770 0.3094 1.49782 82.57 12 −6.1276 0.0666 1.7282528.38 13 1.0685 0.1659 14 2.3462 0.3476 1.49782 82.57 15 −2.1151 D15(variable) 16 14.1546 0.0666 1.58313 59.46 *17 1.3113 D17 (variable) *183.2472 0.3554 1.82080 42.71 19 −5.3219 D19 (variable) 20 ∞ 0.05221.51680 63.88 21 ∞ 0.0166 22 ∞ 0.0777 1.51680 63.88 23 ∞ 0.1554 Imagesurface ∞ [Aspherical surface data] Surface number κ A4 A6 A8 A10 11.0000 −1.22649E−01  8.65627E−02 −2.08158E−02  0.00000E+00 2 0.7707−1.57629E−01 −6.18620E−02  5.29153E−02 −3.20432E−02 3 1.0000−1.30119E−01  3.68681E−03  6.26482E−02  0.00000E+00 4 1.0000−1.21439E−01  7.03803E−02  6.32759E−02 −2.89227E−02 9 1.0000−2.35433E−02  1.06100E−02 −1.16401E−03  3.51134E−03 10 1.0000 3.59908E−02  1.28530E−02  0.00000E+00  0.00000E+00 17 1.0000 3.02388E−02 −1.48125E−03 −8.28950E−02  0.00000E+00 18 1.0000 9.62528E−03  1.36070E−02 −6.11018E−03  0.00000E+00 [Zooming data]Variable Intermediate distance Wide-angle end focal point Telephoto endD7 2.77786 1.51290 0.41986 D15 0.21956 0.55211 1.15116 D17 0.558010.58243 0.56742 D19 0.72522 0.69600 0.73466 [Lens group data] GroupGroup first Group focal Lens configuration number surface length lengthG1 1 −2.08993 1.1098 G2 9 1.75174 1.4816 G3 16 −2.48305 0.0666 G4 182.50378 0.3554 [Conditional expression] Conditional expression (1)D3W/D3T = 0.983 Conditional expression (2) M3/M4 = 0.501 Conditionalexpression (3) BFw/ (fw² + ft²)^(1/2) = 0.394 Conditional expression (4)Σdw/Σdt = 1.275 Conditional expression (5) f4/fw = 2.504 Conditionalexpression (6) (−f1)/f2 = 1.193

Based on Table 5, it is understandable that regarding the zoom lens ZL5according to the present example the conditional expressions (1) to (6)are satisfied.

FIG. 10A to 10C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of zoom lens ZL5 according to Example 5.FIG. 10A illustrates graphs showing various aberrations upon focusing oninfinity in the wide-angle end state of Example 5, FIG. 10B illustratesgraphs showing various aberrations upon focusing on infinity in theintermediate focal length state of Example 5, and FIG. 10C illustratesgraphs showing various aberrations upon focusing on infinity in thetelephoto end state of Example 5. As obvious in each graph showingaberrations, in the zoom lens ZL5 according to Example 5, it isunderstandable that various aberrations are properly corrected, and thishas outstanding optical performance.

Example 6

Example 6 is described using FIGS. 11A to 11C, FIG. 12A to 12C, andTable 6. The zoom lens ZL (ZL6) according to Example 6 is composed of,in order from the object as shown in FIGS. 11A to 11C, a first lensgroup G1 having a negative refractive power, a second lens group G2having a positive refractive power, a third lens group G3 having anegative refractive power, a fourth lens group G4 having a positiverefractive power, a the fifth lens group G5 having a negative refractivepower.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing theimage, a cemented lens composed of a meniscus-shaped positive lens L12having a convex surface facing the image and a biconcave negative lensL13, and a meniscus-shaped positive lens L14 having a convex surfacefacing the object. Note that an image side surface of the negative lensL11 has an aspherical surface.

The second lens group G2 is composed of, in order from the object, anaperture stop S aiming at adjusting a quantity of light, a biconvexpositive lens L21, a cemented lens composed of a meniscus-shapedpositive lens L22 having a convex surface facing the object and ameniscus-shaped negative lens L23 having a concave surface facing theimage, a cemented lens composed of a meniscus-shaped negative lens L24having a concave surface facing the image and a biconvex positive lensL25. Note that both side surfaces of the positive lens L21 have anaspherical surface.

The third lens group G3 is composed of a meniscus-shaped negative lensesL31 having a concave surface facing the image. Note that an image sidesurface of the negative lens L31 has an aspherical surface.

The fourth lens group G4 is composed of a biconvex positive lenses L41.

The fifth lens group G5 is composed of the meniscus-shaped negativelenses L51 having a concave surface facing the object.

The filter group FL is arranged on the image side of the fifth lensgroup G5, and is composed of a low pass filter, an infrared cut filter,etc. for cutting spatial frequency more than marginal resolution of asolid-state image sensing device, such as a CCD disposed on the imagesurface I.

Regarding the zoom lens ZL6 according to the present example, uponzooming from the wide-angle end state (W) to the telephoto end state(T), the lens groups from the first lens group G1 to the fourth lensgroup G4 move so that distances between each lens group change.Specifically speaking, the first lens group G1 once moves to the imageside in a manner of drawing a locus of a convex on the image side, andafterwards moves to the object side. The second lens group G2 moves tothe object side. The third lens group G3 moves to the image side. Thefourth lens group G4 moves to the image side. The fifth lens group G5 isfixed. At this point, a distance between the first lens group G1 and thesecond lens group G2 decreases, a distance between the second lens groupG2 and the third lens group G3 increases, a distance between the thirdlens group G3 and the fourth lens group G4 once increases and afterwardsdecreases, and a distance between the fourth lens group G4 and the fifthlens group G5 decreases.

Values of each data in Example 6 is shown in Table 6 below. The surfacenumbers 1 to 26 in Table 6 correspond to each optical surface of m1 tom26 shown in FIGS. 11A to 11C.

TABLE 6 [General Data] Zoom ratio 2.61 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.58 2.61 Fno 1.82 2.24 2.88 ω 50.1 38.3 23.7Y 1.000 1.187 1.187 BF 0.27 0.27 0.27 TL 9.65 8.88 8.87 [Lens Data]Surface number R D nd νd Object surface ∞  1 4.8166 0.17391 1.6968055.46 *2 1.3044 0.98551  3 −4.6742 0.18814 1.58144 40.98  4 −3.71340.08696 1.58913 61.22  5 4.1774 0.15296  6 3.6921 0.29658 2.00069 25.46 7 13.6501 D7 (variable)  8 ∞ 0.07246 (stop S) *9 1.7540 0.46931 1.7290354.04 *10 −9.9607 0.02899 11 2.6626 0.24556 1.79500 45.31 12 7.18360.08696 1.67270 32.18 13 1.4987 0.22986 14 11.1067 0.16250 1.74950 35.2515 1.2083 0.57971 1.49782 82.57 16 −2.3874 D16 (variable) 17 8.74260.08696 1.58913 61.25 *18 3.0535 D18 (variable) 19 5.7488 0.489761.72916 54.61 20 −4.0596 D20 (variable) 21 −6.5217 0.08696 1.48749 70.3222 −28.3863 0.02899 23 ∞ 0.06834 1.51680 63.88 24 ∞ 0.02181 25 ∞ 0.101781.51680 63.88 26 ∞ 0.04657 Image surface ∞ [Aspherical surface data]Surface number κ A4 A6 A8 A10 2 0.6272 −2.52625E−03  3.72198E−03−2.73998E−03 1.00790E−03 9 1.0000 −1.83548E−02 −1.20683E−04 −5.71472E−040.00000E+00 10 1.0000  1.92507E−02  2.52728E−04  0.00000E+00 0.00000E+0018 1.0000  2.44010E−02 −1.99545E−03 −2.01356E−04 0.00000E+00 [Zoomingdata] Variable Intermediate distance Wide-angle end focal pointTelephoto end D7 3.19934 1.67813 0.47826 D16 0.10145 0.86729 2.25232 D180.79242 0.93415 0.79035 D20 0.86838 0.71292 0.66119 [Lens group data]Group Group first Group focal Lens configuration number surface lengthlength G1 1 −2.21265 1.88406 G2 9 2.40024 1.87535 G3 17 −8.01041 0.08696G4 19 3.33333 0.48976 G5 21 −17.39131 0.08696 [Conditional expression]Conditional expression (1) D3W/D3T = 1.003 Conditional expression (2)M3/M4 = 0.990 Conditional expression (3) BFw/( fw² + ft²)^(1/2) = 0.096Conditional expression (4) Σdw/Σdt = 1.091 Conditional expression (5)f4/fw = 3.333 Conditional expression (6) (−f1)/f2 = 0.922

Based on Table 6, it is understandable that in the zoom lens ZL6according to the present example the conditional expressions (1) to (6)are satisfied.

FIG. 12A to 12C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of the zoom lens ZL6 according to Example6. FIG. 12A illustrates graphs showing various aberrations upon focusingon infinity in the wide-angle end state of Example 6, FIG. 12Billustrates graphs showing various aberrations upon focusing on infinityin the intermediate focal length state of Example 6, and FIG. 12Cillustrates graphs showing various aberrations upon focusing on infinityin the telephoto end state of Example 6. As is obvious in each graphshowing aberrations, in the zoom lens ZL6 according to Example 6, it isunderstandable that various aberrations are properly corrected, and thishas outstanding optical performance.

Example 7

Example 7 is described using FIGS. 13A to 13C, FIG. 14A to 14C, andTable 7. The zoom lens ZL (ZL7) according to Example 7 is composed of,in order from the object as shown in FIGS. 13A to 13C, a first lensgroup G1 having a negative refractive power, a second lens group G2having a positive refractive power, a third lens group G3 having anegative refractive power, and a fourth lens group G4 having a positiverefractive power.

The first lens group G1 is composed of, in order from the object, ameniscus-shaped negative lens L11 having a concave surface facing theimage, a biconcave negative lens L12, and a meniscus-shaped positivelens L13 having a convex surface facing the object. Note that both sidesurfaces of the negative lens L11 have an aspherical surface. Moreover,both side surfaces of the negative lens L12 have an aspherical surface.

The second lens group G2 is composed of, in order from the object, anaperture stop S aiming at adjusting a quantity of light, a biconvexpositive lens L21, a cemented lens composed of a biconvex positive lensL22 and a biconcave negative lens L23, and a biconvex positive lens L24.Note that both side surfaces of the positive lens L21 have an asphericalsurface.

The third lens group G3 is composed of, in order from the object, acemented lenses composed of a meniscus-shaped positive lens L31 having aconvex surface facing the object and a meniscus-shaped negative lens L32having a concave surface facing the image. Note that an image sidesurface of the negative lens L32 has an aspherical surface.

The fourth lens group G4 is composed of an biconvex positive lenses L41.Note that an object side surface of the positive lens L41 has anaspherical surface.

The filter group FL is arranged on the image side of the fourth lensgroup G4, and is composed of a low pass filter, an infrared cut filter,etc. for cutting spatial frequency more than marginal resolution of asolid-state image sensing device, such as a CCD disposed on the imagesurface I.

Regarding the zoom lens ZL7 according to the present example, uponzooming from the wide-angle end state (W) to the telephoto end state(T), all lens groups from the first lens group G1 to the fourth lensgroup G4 move so that distances between each lens group change.Specifically speaking, the first lens group G1 moves to the image side.The second lens group G2 moves to the object side. The third lens groupG3 moves to the object side. The fourth lens group G4 once moves to theimage side in a manner of drawing a locus of a convex, and afterwardsmoves to the object side. At this point, a distance between the firstlens group G1 and the second lens group G2 decreases, a distance betweenthe second lens group G2 and the third lens group G3 increases, and adistance between the third lens group G3 and the fourth lens group G4increases.

Values of each data in Example 7 is shown in Table 7 below. The surfacenumbers 1 to 23 in Table 7 correspond to each optical surface of m1 tom23 indicated in FIGS. 13A to 13C.

TABLE 7 [General Data] Zoom ratio 2.23 Intermediate Wide-angle end focalpoint Telephoto end f 1.00 1.46 2.23 Fno 1.85 2.40 2.81 ω 41.6 33.7 22.1Y 0.772 0.917 0.917 BF 1.10 1.04 1.11 TL 7.53 6.67 6.23 [Lens Data]Surface number R D nd νd Object surface ∞ *1 2.0842 0.0895 1.69680 55.46*2 0.8578 0.6965 *3 −3.2981 0.0895 1.59201 67.02 *4 67.1703 0.0253  52.3534 0.2184 1.92286 20.88  6 3.8951 D6 (variable)  7 ∞ 0.0560 (stop S)*8 1.4438 0.4477 1.77250 49.50 *9 −6.4742 0.0728 10 2.2805 0.26301.49782 82.57 11 −8.3399 0.0672 1.72825 28.38 12 1.0551 0.2864 13 2.62280.3685 1.49782 82.57 14 −1.9670 D14 (variable) 15 5.1461 0.1254 1.8348142.73 16 7.0228 0.0672 1.74330 49.32 *17 1.3713 D17 (variable) *183.5373 0.2988 1.82080 42.71 19 −7.3787 D19 (variable) 20 ∞ 0.05261.51680 63.88 21 ∞ 0.0168 22 ∞ 0.0784 1.51680 63.88 23 ∞ 0.1567 Imagesurface ∞ [Aspherical surface data] Surface number κ A4 A6 A8 A10 11.0000 −1.38024E−01  6.05393E−02 −1.61893E−02  0.00000E+00 2 0.4953−1.16727E−01 −2.94793E−02  1.54379E−02 −2.27592E−02 3 1.0000−9.06410E−03 −6.32774E−02  7.07144E−02  0.00000E+00 4 1.0000−2.60980E−02 −4.23139E−02  8.78300E−02 −2.67685E−02 8 1.0000−3.18339E−02  3.08040E−03  5.07463E−03 −3.24715E−03 9 1.0000 4.26824E−02  5.47004E−03  0.00000E+00  0.00000E+00 17 1.0000 2.83947E−02  2.97098E−02 −8.57895E−02  0.00000E+00 18 1.0000 1.50043E−02  2.20033E−02 −9.59971E−03  0.00000E+00 [Zooming data]Variable Intermediate distance Wide-angle end focal point Telephoto endD6 2.70737 1.47742 0.46339 D14 0.08955 0.44531 1.01706 D17 0.461960.53835 0.47206 D19 0.83986 0.77842 0.84998 [Lens group data] GroupGroup first Group focal Lens configuration number surface length lengthG1 1 −1.98768 1.1192 G2 8 1.76777 1.5616 G3 15 −2.60713 0.1926 G4 182.94947 0.2988 [Conditional expression] Conditional expression (1)D3W/D3T = 0.979 Conditional expression (2) M3/M4 = 0.501 Conditionalexpression (3) BFw/(fw² + ft²)^(1/2) = 0.450 Conditional expression (4)Σdw/Σdt = 1.255 Conditional expression (5) f4/fw = 2.949 Conditionalexpression (6) (−f1)/f2 = 1.124

Based on FIG. 7 , it is understandable that regarding the zoom lens ZL7according to the present example, the conditional expressions (1) to (6)are satisfied.

FIG. 14A to 14C illustrate graphs showing various aberrations (sphericalaberration, astigmatism, distortion aberration, coma aberration, andlateral chromatic aberration) of zoom lens ZL7 according to Example 7.FIG. 14A illustrates graphs showing various aberrations upon focusing oninfinity in the wide-angle end state of Example 7, FIG. 14B illustratesgraphs showing various aberrations upon focusing on infinity in theintermediate focal length state of Example 7, and FIG. 14C illustratesgraphs showing various aberrations upon focusing on infinity in thetelephoto end state of Example 7. As is obvious in each graph showingaberrations, in the zoom lens ZL7 according to Example 7, it isunderstandable that various aberrations are properly corrected, and thishas outstanding optical performance.

According to each example above, although it is small, an angle of viewin the wide-angle end state is approximately 84 degrees, thus it ispossible to provide a zoom lens having outstanding optical performance.

In order to have the present invention understandable, elements of theembodiment were attached and explained, however the present invention isnot limited to the above.

For instance, in the examples above four groups and five groupconfigurations are exampled, however, this is applicable to anothergroup. Moreover, this is applicable to a configuration in which a lensor a lens group is added closest to the object, or a configuration inwhich a lens or a lens group is added closest to the image. Moreover, alens group means a part that has at least one lens separated at an airinterval which changes at the time of focusing or zooming.

Moreover, it is appreciated that a focusing lens group is configured tofocus on a short distance object from an infinity object by moving asingle or a plurality of lens group(s), or a partial lens group in anoptical axis direction. This focusing lens group is also applicable toautofocus, and is also suitable for motor drive for autofocus (using anultrasonic motor, etc.). In particular, it is preferable that the thirdlens group G3 or the fourth lens group G4 is used as a focusing lensgroup. Or, it is also possible to perform focusing by synchronouslymoving the third lens group G3 and the fourth lens group G4.

Moreover, it is appreciated a vibration control lens group is configuredto move a lens group or a partial lens group in manner of having acomponent in a direction perpendicular to the axis direction, or rotateand move (swing) it in a direction within a surface including the axisdirection so that image blur due to camera shake is corrected. Inparticular, it is preferable that the second lens group G2 or the thirdlens group G3 is used as a vibration control lens group.

Moreover, it is also appreciated that a lens surface is formed with aspherical surface or a plane, or formed in an aspherical surface. Incase a lens surface has a spherical surface or a plane, it is possibleto easily have lens processing and an assembly adjustment, and toprevent degradation of optical performance due to errors of theprocessing and the assembly adjustment, and it is preferable. Moreover,it is preferable because there is less degradation of the depictionperformance when an image surface is shifted. In case a lens surface hasan aspherical surface, it is appreciated that the aspherical surface isformed as any one of an aspherical surface which is formed throughgrinding processing, a glass mold aspherical surface which glass isformed into a aspherical surface configuration using a mold, and acomplexed aspherical surface which a resin is formed on a surface ofglass and formed in a aspherical surface configuration. Moreover, it isappreciated that a lens surface is formed as a diffractive surface,additionally a lens is formed as a graded-index lens (GRIN lens) or aplastic lens.

The aperture stop S is preferable to be disposed near the second lensgroup G2, however this is substituted using a frame of a lens instead ofproviding a member as an aperture stop.

It is appreciated a reflection reducing film having high transmissivityin a wide wavelength band is formed on each lens surface in order toreduce flare and ghosting and attain high optical performance with highcontrast.

EXPLANATION OF NUMERALS AND CHARACTERS

-   -   ZL (ZL1 to ZL7) Zoom lens    -   G1 First lens group    -   G2 Second lens group    -   G3 Third lens group    -   G4 Fourth lens group    -   G5 Fifth lens group    -   S Aperture stop    -   FL Filter group    -   I Image surface    -   CAM Digital still camera (optical apparatus)

This is a continuation of PCT International Application No.PCT/JP2014/005687, filed on Nov. 12, 2014, which is hereby incorporatedby reference. This application also claims the benefit of JapanesePatent Application Nos. 2013-240958 filed in Japan on Nov. 21, 2013 and2014-174637 filed in Japan on Aug. 28, 2014, which are herebyincorporated by reference.

The invention claimed is:
 1. A zoom lens comprising, in order from anobject, a first lens group having a negative refractive power, a secondlens group having a positive refractive power, a third lens group havinga negative refractive power, and a fourth lens group, the first lensgroup, the second lens group, the third lens group, and the fourth lensgroup moving on an optical axis so that zooming is performed by changingrespective distances between the first lens group and the second lensgroup, the second lens group and the third lens group, and the thirdlens group and the fourth lens group, the first lens group comprising anegative lens disposed closest to the object, and a negative lens, andthe following conditional expressions being satisfied:0.30<D3W/D3T<1.101.00<Σdw/Σdt<1.550.80<(−f1)/f2<1.500.50<M4/M3<1.00 where D3W denotes an air interval between the third lensgroup and the fourth lens group in a wide-angle end state, D3T denotesan air interval between the third lens group and the fourth lens groupin a telephoto end state, Σdw denotes a distance from a front end lenssurface to a rear end lens surface of the zoom lens in the wide-angleend state, Σdt denotes a distance from the front end lens surface to therear end lens surface of the zoom lens in the telephoto end state, f1denotes a focal length of the first lens group, f2 denotes a focallength of the second lens group, M3 denotes an amount of movement on theoptical axis of the third lens group upon zooming from the wide-angleend state to the telephoto end state, and M4 denotes an amount ofmovement on the optical axis of the fourth lens group upon zooming fromthe wide-angle end state to the telephoto end state.
 2. A zoom lensaccording to claim 1, wherein the following conditional expression issatisfied:0.05<BFw/(fw ² +ft ²)^(1/2)<0.50 where BFw denotes an air equivalentdistance from a rear end lens surface of the zoom lens in the wide-angleend state to an image surface, fw denotes a focal length of the zoomlens in the wide-angle end state, and ft denotes a focal length of thezoom lens in the telephoto end state.
 3. A zoom lens according to claim1, wherein the third lens group is composed of a cemented lens having anegative refractive power.
 4. A zoom lens according to claim 1, whereinthe second lens group includes a positive lens closest to the object. 5.A zoom lens according to claim 1, wherein the second lens group includesa positive lens closest to the object, and wherein the positive lens hasan aspherical surface.
 6. An optical apparatus including the zoom lensaccording to claim
 1. 7. A method for manufacturing a zoom lens,comprising: arranging in a lens barrel, in order from an object, a firstlens group having a negative refractive power, a second lens grouphaving a positive refractive power, a third lens group having a negativerefractive power, and a fourth lens group, the arranging being such thatthe first lens group, the second lens group, the third lens group, andthe fourth lens group are movable on an optical axis so that zooming isperformed by changing respective distances between the first lens groupand the second lens group, the second lens group and the third lensgroup, and the third lens group and the fourth lens group, configuringthe first lens group to comprise a negative lens disposed closest to theobject, and a negative lens, and satisfying the following conditionalexpressions:0.30<D3W/D3T<1.101.00<Σdw/Σdt<1.550.80<(−f1)/f2<1.500.50<M4/M3<1.00 where D3W denotes an air interval between the third lensgroup and the fourth lens group in a wide-angle end state, D3T denotesan air interval between the third lens group and the fourth lens groupin a telephoto end state, Σdw denotes a distance from a front end lenssurface to a rear end lens surface of the zoom lens in the wide-angleend state, Σdt denotes a distance from the front end lens surface to therear end lens surface of the zoom lens in the telephoto end state, f1denotes a focal length of the first lens group, f2 denotes a focallength of the second lens group, M3 denotes an amount of movement on theoptical axis of the third lens group upon zooming from the wide-angleend state to the telephoto end state, and M4 denotes an amount ofmovement on the optical axis of the fourth lens group upon zooming fromthe wide-angle end state to the telephoto end state.